At least 50

During the Cold War, some nations preferred to remain neutral by not aligning themselves with the West (NATO) or the East(Communist Bloc). Such countries were called Third World countries. Today, however, the term is used to refer to poor or developing countries.

There are around 50 third world countries in terms of Poverty, around 45 countries have a low human development index and 16 countries have an average yearly income/capita that is less than $1000.

The usage of the term  ‘third world’  has become less preferable in recent years as several countries are struggling to gain steady economic development.